JP2012222006A - Solar cell, and manufacturing method of solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell in which the open voltage is increased when compared with a conventional solar cell and, as a result, the conversion efficiency is increased.SOLUTION: The solar cell has a first light absorption layer 10, and a second light absorption layer 12. The first light absorption layer 10 is a p-type semiconductor layer containing a group Ib element, a group IIIb element, and a group VIb element and including a luminescence peak having a half value width of 1 meV or more and 15 meV or less in photoluminescence spectrum or cathode luminescence spectrum. The second light absorption layer 12 contains a group Ib element, a group IIIb element, and a group VIb element, where the composition ratio of the group Ib element and the group IIIb element is 0.1 or more and less than 1.0, and the second light absorption layer 12 is provided on the light incident surface side of the first light absorption layer.

Description

  The present invention relates to a solar cell and a method for manufacturing a solar cell.

In place of the bulk crystal silicon solar cells that have been widely used, development of solar cells using a thin film semiconductor layer as a light absorption layer is in progress. Among them, an element selected from group Ib of the periodic table such as Cu, Ag or Au, an element selected from group IIIb of the periodic table such as In, Ga or Al, and a group VIb of the periodic table such as O, S, Se or Te are selected. A thin film solar cell using a compound semiconductor layer containing an element as an absorption layer exhibits high energy conversion efficiency and is less affected by light degradation, and thus is expected as a next-generation solar cell. Specifically, CuInSe ₂ (hereinafter referred to as CISe) composed of Cu, In, and Se, or Cu (In, Ga) Se ₂ (hereinafter referred to as CIGSe) in which a part of In that is a group IIIb is replaced with Ga is used. High conversion efficiency is obtained in the thin film solar cell using the chalcopyrite p-type semiconductor film as a light absorption layer. In particular, it is said that high conversion efficiency can be obtained by using a vapor deposition method called a three-stage method. (See Non-Patent Document 1)

Prog. Photovolt: Res. Appl. (2008), 16: 235-239. Wide-Gap Chalcopyrites (Springer Series in MATERIALS SCIENCE) p. 146 Applied Physics Letters 63 (24) (1993) p. 3294 Wide-Gap Chalcopyrites (Springer Series in MATERIALS SCIENCE) p. 130

The stoichiometric composition ratio of the Ib group element and the IIIb group element in the chalcopyrite p-type semiconductor is Ib composition (atomic%) / IIIb composition (atomic%) = 1.0, respectively. Hereinafter, Ib composition (atomic%) / IIIb composition (atomic%) <1.0 is referred to as Ib-poor composition, and Ib composition (atomic%) / IIIb (atomic%)> 1.0 is referred to as Ib-rich composition. In a solar cell using a general chalcopyrite p-type light absorption layer, the light absorption layer is adjusted to an Ib-poor composition and used. This is because when the Ib / IIIb element ratio in the light absorption layer exceeds the stoichiometric composition ratio and becomes the Ib-rich composition, precipitation of a compound between the Ib group element and the VIb group element which is a different phase, IbxVIb starts. As an example, FIG. 3 shows an equilibrium phase diagram between Cu ₂ Se and In ₂ Se ₃ . This different phase IbxVIb is a highly conductive material. If this different phase is present in the light absorption layer, the lower back electrode layer and the upper n-type semiconductor layer are short-circuited, and the solar cell characteristics are greatly deteriorated. Therefore, a chalcopyrite p-type semiconductor film having an Ib-rich composition has not been generally used as a light absorption layer.

  On the other hand, there is a report that a chalcopyrite p-type semiconductor film having an Ib-rich composition has superior electrical characteristics as compared with a film having an Ib-poor composition (see Non-Patent Document 2). According to Non-Patent Document 2, a CIGSe film formed with a Cu-rich composition has a low defect density. When this film is used for a light absorption layer of a solar cell, it is considered that high conversion efficiency can be obtained because of the high transport property of photogenerated carriers. However, as described above, CISe, CGSe, and CIGSe having a Cu-rich composition have CuxSe that is a different phase at the same time, thereby making it impossible to make use of the good carrier transport characteristics of the original Cu-rich composition film.

  In order to solve this problem, there is a technique for selectively removing IbxSe which is a different phase (see Non-Patent Document 3). In this technique, only the Ib group element-VIb group element compound which is selectively in a different phase by being immersed in an aqueous potassium cyanide (KCN) solution is etched from the film. Thereby, only the chalcopyrite p-type semiconductor film formed with the Ib-rich composition can be used as the light absorption layer. However, even if a solar cell is produced using this KCN-etched light absorption layer, that is, a light absorption layer that does not have a conductive IbxSe layer that is a different phase, the characteristics are improved as compared with those before the etching. The high open-circuit voltage expected from the good carrier transport property of the Ib-rich composition film cannot be obtained, and the conversion efficiency is low.

  In general, when a semiconductor material is irradiated with light or an electron beam, light emission called photoluminescence (hereinafter referred to as PL) and cathode luminescence (hereinafter referred to as CL) is obtained. Similar light emission can be obtained in the chalcopyrite p-type semiconductor film used for the light absorption layer of the solar cell. The chalcopyrite semiconductor used for the light absorption layer is usually a p-type semiconductor having holes as majority carriers, but has both an acceptor that forms holes and a donor that forms electrons. The shapes of the PL spectrum and the CL spectrum vary depending on various factors. One of the factors is the donor concentration and the acceptor concentration. These luminescences are energy transitions between two levels, for example, the conduction band bottom energy level--the valence band top energy level, the donor level-acceptor level, and the energy level formed by free excitons- It occurs between valence band top energy levels. The majority carrier of the p-type semiconductor is a hole. However, when the majority carrier (electron) is compensated for the majority carrier (hole), the full width at half maximum of the PL spectrum and the CL spectrum increases. This is because the energy level distribution described above fluctuates, the energy between the energy levels changes, and light emission with various energies overlaps.

  As described above, the PL and CL spectra strongly depend on the state of energy levels existing in the semiconductor material. When a p-type semiconductor film capable of observing PL and CL with a narrow half-value width is used for the light absorption layer, the fluctuation of the energy level described above is small, so the probability of carrier recombination decreases and the transport characteristics of photogenerated carriers increase. . This can be expected to improve conversion efficiency.

  It is known that the half width of the PL spectrum at the time of low temperature (10K or less) measurement in a chalcopyrite p-type semiconductor is affected by the Ib group / IIIb group composition ratio (see Non-Patent Document 4). Usually, in the Ib-rich composition, exciton emission with a narrow half-value width is obtained.

  As described above, one of the factors contributing to the half width of the PL or CL spectrum is the degree of fluctuation of the energy level. In addition to Ib-rich, by reducing Se vacancies by crystal growth under a high partial pressure of selenium, or by reducing the concentration of sodium mixed in the film, the carrier compensation effect is reduced, and PL or CL with a narrow half-value width Can be obtained. However, even if a solar cell is prepared using this light absorption layer having a narrow half-value width PL produced by any method, the high conversion efficiency expected from good carrier transport characteristics cannot be obtained.

  The present inventors have obtained PL or CL with a narrow half-value width, and have good carrier transport characteristics despite using a light absorbing layer in which a highly conductive heterogeneous phase is selectively removed from the light absorbing layer. It has been found that there are the following problems as the reason why the conversion efficiency cannot be improved because it cannot be utilized.

As an example of solar cell characteristics when a chalcopyrite p-type semiconductor having a narrow half-value width PL or CL and containing no heterogeneous phase is used for the light absorption layer of the solar cell, the following is shown for KCN-CuCuSeSe ₂ reverse saturation current density j ₀ and the parallel resistance R _P and the open voltage Voc of the solar cell using a layer to remove CuxSe a heterogeneous phase by performing etching as the light-absorbing layer, the short-circuit current density Jsc, fill factor FF, the conversion An example of the value of efficiency η is shown. In addition, the half width of the PL spectrum at 10 K (Kelvin) of this layer was 7 meV, and the half width of the CL spectrum was 7 meV.
j ₀ : 5.11 × 10 ⁻⁸ (A / cm ² ), R _P : 185 (Ω · cm),
V _OC : 0.400 (V), J _SC : 33.5 (mA / cm ² ),
FF: 0.603, η: 8.08 (%)

A CuInSe ₂ solar cell with high conversion efficiency generally has a _value of j _{0 on the order} of 10 ⁻⁷ to 10 ⁻¹¹ (A / cm ² ) and a value of Rp of 500 (Ω · cm) or more. In comparison, a solar cell using the Cu-rich CuInSe ₂ thin film as a light absorbing layer is larger value of _{j 0} It can be seen that the value of _{R P} is small.

ｊ：電流密度
ｊ₀：逆方向飽和電流密度
ｊ_ｐｈ：光電流密度
ｅ：電気素量
Ｖ：電圧
Ａ：理想ダイオード因子
ｋ_Ｂ：ボルツマン定数
Ｔ：温度
Ｒ_Ｓ：直列抵抗
Ｒ_Ｐ：並列抵抗 In general, an equivalent circuit of a pn junction solar cell is represented by the following formula (1). This model is hereinafter referred to as a single diode model.

j: current density j ₀ : reverse saturation current density j _ph : photocurrent density e: elementary electric charge V: voltage A: ideal diode factor k _B : Boltzmann constant T: temperature R _S : series resistance R _P : parallel resistance

Here, in order to clarify the cause of the low _{VOC of} a solar cell using a Cu-rich CuInSe ₂ thin film as a light-absorbing layer, in which PL and CL with a narrow half-value width are obtained and KCN etching for removing a different phase is performed. A simulation was performed using Equation 1. As a parameter indicating the results of the case of changing the j ₀ in FIG. 5 results in the case of changing the Figure 4, Rp. The present inventors have found from this result that the cause of the low V _OC is that the reverse saturation current j ₀ is large.

In general, in a pn junction type semiconductor solar cell, the reverse saturation current j ₀ is said to be caused by recombination of photogenerated carriers in the depletion layer or recombination of photogenerated carriers at the pn junction interface. ing. Therefore, it is considered that the main factor that the efficiency of the solar cell using the Ib-rich chalcopyrite light absorption layer subjected to KCN etching is low is the recombination of photogenerated carriers in the vicinity of the junction.

As described above, a single layer is a chalcopyrite p-type semiconductor film that is expected to have high carrier transport characteristics that can provide PL and CL with good electrical characteristics and narrow half-value widths. Even when a solar cell is formed, high conversion efficiency is not achieved because recombination of photogenerated carriers at the junction interface with the n-type semiconductor layer is high and it is difficult to obtain high V _OC .

  In order to achieve the above object, a solar cell according to the present invention includes a group Ib element, a group IIIb element, and a group VIb element, and emits light having a half width of 1 meV or more and 15 meV or less in a photoluminescence spectrum or cathodoluminescence spectrum. A first light absorption layer which is a p-type semiconductor layer including a peak, includes a group Ib element, a group IIIb element, and a group VIb element, and a composition ratio of the group Ib element to the group IIIb element is 0.1 or more; A second light absorption layer that is less than 0 is provided on the first light absorption layer.

  According to the present invention, an open-circuit voltage is higher than that of a conventional solar cell having only a p-type semiconductor layer including a light emission peak having a half-value width of 1 meV or more and 15 meV or less in a photoluminescence spectrum or a cathodoluminescence spectrum as a light absorption layer. As a result, the conversion efficiency can be increased.

  The inventors of the present invention are a p-type semiconductor layer in which the second light-absorbing layer having the Ib-poor composition is a p-type semiconductor layer including a light emission peak having a half-value width of 1 meV or more and 15 meV or less in a photoluminescence spectrum or a cathodoluminescence spectrum. By forming on one p-type light absorption layer and forming an n-type semiconductor layer thereon, recombination of photogenerated carriers at the pn junction interface can be reduced, resulting in the effects of the present invention. I think. Specific reasons are shown below.

FIG. 6 is a schematic diagram of a band structure of a solar cell provided with only a p-type semiconductor layer including a light emission peak having a half-value width of 1 meV or more and 15 meV or less in a conventional photoluminescence spectrum or cathodoluminescence spectrum as a light absorption layer. The schematic of an example of the band structure of the solar cell obtained by this invention is shown. As shown in FIG. 7, the band gap of the light absorption layer surface can be expanded by the second light absorption layer. This is because the valence band bottom energy position (E _V ) is lower than that of the first light absorption layer. Thus, this region serves as a barrier layer against hole injection at the junction interface with the n-type semiconductor layer, and recombination of photogenerated carriers at the junction interface can be reduced. As a result, the effect of the present invention can be obtained.

  In the said invention, it is preferable that the composition ratio of the Ib group element and the IIIb group element contained in said 1st light absorption layer is 1.0. When the Ib group element / IIIb group element ratio is larger than 1.0, the conductive Ibx group-VIb group compound, which is a different phase, is precipitated, the solar cell element is short-circuited and the characteristics are easily deteriorated, and the effect of the present invention is reduced. Tend. If it is less than 1.0, the aforementioned fluctuation of the energy level tends to be large, and the effect of the present invention tends to be small.

  In the present invention, the Ib group element and the IIIb group element contained in the second light absorption layer are preferably the same as the Ib group element and the IIIb group element contained in the first light absorption layer. Thereby, the effect of the present invention becomes remarkable.

  In the said invention, it is preferable that the Ib group element contained in said 1st light absorption layer and 2nd light absorption layer is Cu. Thereby, the effect of the present invention becomes more remarkable.

  In the said invention, it is preferable that the thickness of the 2nd light absorption layer formed on said 1st light absorption layer is the range of 1 nm or more and 100 nm or less. As a result, the effect of the present invention becomes more remarkable.

で表したとき１＜ｋ＜２であることが好ましい。これにより本発明の効果は顕著となる。 The relationship between the excitation light intensity I _ex ^k and the photoluminescence intensity I _PL when the excitation light dependency is measured in the photoluminescence measurement is expressed by the following equation (2).

It is preferable that 1 <k <2. Thereby, the effect of the present invention becomes remarkable.

  It is preferable that the manufacturing process of the first light absorption layer includes a step of removing an excessively precipitated lb group-VIb group compound after the lb-rich growth once. Thereby, the intermetallic compound of group Ib-VIb which is a different conductive phase can be removed from the light absorption layer, and the effect of the present invention becomes remarkable.

  The second light absorption layer is preferably formed by a kind of method selected from a vacuum deposition method and a sputtering method. This makes it possible to form a second light absorption layer that has a uniform composition and film thickness distribution easily over a large area and has few impurity components that cause deterioration in characteristics, and thus the effect of the present invention becomes remarkable.

  The second light absorption layer is preferably formed by performing a heat treatment in a subsequent step in addition to a kind of method selected from a vacuum deposition method and a sputtering method. This makes it possible to accurately control the amount of Ib group diffusion from the first p-type light absorption layer to the second light absorption layer, and to accurately set the thickness of the second light absorption layer. Since the control becomes possible, the effect of the present invention becomes remarkable.

  According to the present invention, the open-circuit voltage is higher than that of a conventional solar cell including a light-absorbing layer of a chalcopyrite p-type semiconductor film including a light emission peak having a half-value width of 1 meV or more and 15 meV or less in a photoluminescence spectrum or a cathodoluminescence spectrum. It is possible to provide a solar cell that can increase the conversion efficiency as a result, and a method for manufacturing the solar cell.

It is a schematic sectional drawing of a solar cell provided with the chalcopyrite p-type semiconductor film containing the light emission peak whose half value width is 1 meV or more and 15 meV or less in the conventional photoluminescence spectrum or cathodoluminescence spectrum as a light absorption layer. It is a schematic sectional drawing of the solar cell which concerns on one Embodiment of this invention. It is an equilibrium state phase diagram between Cu ₂ Se and In ₂ Se ₃ . assumes a single diode model in the pn junction solar cell, a simulation result of current-voltage characteristics when the reverse saturation current j ₀ as a parameter. assumes a single diode model in the pn junction solar cell, a simulation result of current-voltage characteristics when the parallel resistance component R _P as a parameter. It is the schematic of the band structure of a solar cell provided with the chalcopyrite p-type semiconductor film containing the light emission peak whose half value width is 1 meV or more and 15 meV or less in the conventional photoluminescence spectrum or cathodoluminescence spectrum. It is the schematic of an example of the band structure of the solar cell obtained by this invention.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals. Also, the positional relationship between the top, bottom, left and right is as shown in the drawing. Further, when the description overlaps, the description is omitted.

(Solar cell)
As shown in FIG. 2, the solar cell 4 according to this embodiment includes a soda lime glass 6, a back electrode layer 8 formed on the soda lime glass 6, and a first electrode formed on the back electrode layer 8. a p-type light absorption layer 10, a second light absorption layer 12 formed on the first p-type light absorption layer 10, an n-type buffer layer 14 formed on the second light absorption layer 12, A semi-insulating layer 16 formed on the n-type buffer layer 14, a window layer 18 (transparent conductive layer) formed on the semi-insulating layer 16, and an upper electrode 20 (extraction electrode) formed on the window layer 18 And a thin film solar cell.

  The first p-type absorber layer 10 is composed of a group Ib element such as Cu, Ag or Au, a group IIIb element such as In, Ga or Al, and a group VIb element such as O, S, Se or Te. It is a p-type compound semiconductor layer.

  The second light absorption layer 12 formed on the first p-type light absorption layer 10 includes a group Ib element such as Cu, Ag, or Au, a group IIIb element such as In, Ga, or Al, and further O, S. , Se or Te, and the like.

  The photoluminescence spectrum or cathodoluminescence spectrum of the first p-type light absorption layer 10 includes an emission peak whose half-value width of the emission peak is 1 meV or more and 15 meV or less. This emission spectrum is observed at a low temperature of 10K (Kelvin) or less.

  When the half width of the photoluminescence spectrum or cathodoluminescence spectrum obtained from the first p-type light absorption layer 10 is larger than 15 meV, the carrier transport property of the p-type light absorption layer is deteriorated, and the effect of the present invention is obtained. It becomes impossible.

  When the half width of the photoluminescence spectrum or cathodoluminescence spectrum obtained from the first p-type light absorption layer 10 is smaller than 1 meV, it is difficult to detect and cannot be distinguished from noise.

  In the following, the ratio of the lb group element content (atomic%) to the IIIb group element content (atomic%) in the first p-type light absorbing layer 10 or the second light absorbing layer 12 is expressed as lb group element / IIIb. It is written as group element ratio.

  The second light-absorbing layer 12 formed on the first p-type light-absorbing layer 10 containing this light emission is an Ib group element such as Cu, Ag or Au, an IIIb group element such as In, Ga or Al, and It is a layer composed of a VIb group element such as O, S, Se or Te. The Ib group element / IIIb group element ratio in the second light absorption layer 12 is 0.1 or more and less than 1.0. When the ratio of the group Ib element / group IIIb element contained in the second light absorption layer is smaller than 0.1, a compound is formed only between the group IIIb element and the group VIb element, hindering light absorption and carrier transport, It will deteriorate. When the Ib group element / IIIb group element ratio is larger than 1.0, a conductive compound is generated between the Ib group element and the VIb group element, and the characteristics deteriorate. Further, since the band gap energy becomes the same as that of the first p-type light absorption layer 10, it does not serve as the intended hole barrier layer, and the effect of the present invention cannot be obtained.

  The Ib group element / IIIb group element ratio in the first p-type absorber layer 10 is preferably 1.0. When the Ib group element / IIIb group element ratio is larger than 1.0, the conductive Ibx group-VIb group compound, which is a different phase, is precipitated, the solar cell element is short-circuited and the characteristics are easily deteriorated, and the effect of the present invention is reduced. Tend. If it is less than 1.0, the aforementioned fluctuation of the energy level tends to be large, and the effect of the present invention tends to be small.

  The Ib group element and the IIIb group element contained in the second light absorption layer 12 formed on the first p type light absorption layer 10 are the Ib group element and IIIb contained in the first p type light absorption layer 10. It is preferably the same as the group element. Moreover, when using several Ib group elements for each layer, it is preferable that the ratio is also the same. Similarly, when a plurality of group IIIb elements are used in each layer, the ratio is preferably the same. This makes it easier to obtain the effects of the present invention.

  The Ib group element and IIIb group element contained in the second light absorption layer 12 formed on the first p type light absorption layer 10 are the Ib group element and IIIb group contained in the first p type light absorption layer 10. When not the same as the element, the band gap energy of the first p-type absorber layer 10 and the second absorber layer 12 is different. This is mainly due to the change in the position of the conduction band bottom energy Ec. When the position of the conduction band bottom energy Ec of the second light absorption layer 12 is smaller than the first p-type light absorption layer 10, the recombination of majority carriers increases through the defect level at the junction interface and the open circuit voltage decreases. Resulting in. On the other hand, when the position of the conduction band bottom energy Ec of the second light absorption layer 12 is larger than that of the first p-type light absorption layer 10, this energy difference works as a barrier for photogenerated carriers. As a result, the number of carriers that can be taken out decreases, and the short circuit current density Jsc decreases.

  When the group Ib element contained in the first p-type light absorption layer 10 and the second light absorption layer 12 is Cu, the band gap energy of both layers is in a wide range from about 1.0 eV to about 3.5 eV. It can be adjusted and is preferable. When the group VIb element contained in the first p-type light absorption layer 10 is Se, the group III element is preferably an element selected from In or Ga, or In and Ga, or a combination of In and Al. Thereby, it is possible to adjust the band gap energy, which is considered to be suitable as a light absorption layer for solar cells, between about 1.0 eV to about 1.8 eV. When the VIb group element contained in the first p-type light absorption layer 10 is S, the IIIb group element is preferably In or a combination of In and Ga. Thereby, it is possible to adjust the band gap energy, which is considered to be suitable as a light absorption layer for solar cells, between about 1.0 eV to about 1.8 eV.

  The thickness of the second light absorption layer formed on the first p-type light absorption layer 10 is preferably 1 nm or more and 100 nm or less. When the thickness is smaller than 1 nm, the function as a hole injection barrier layer is deteriorated due to a tunneling phenomenon. Moreover, since it is too thin, formation is difficult. When the thickness is larger than 100 nm, carrier recombination occurs in the second light absorption layer, and the characteristics tend to deteriorate.

で表したとき 、ｋは１＜ｋ＜２であることが好ましい。 The relationship between the excitation light intensity or the excitation electron beam intensity I _ex ^k and the photoluminescence intensity I _PL when the excitation light dependency or the excitation electron beam intensity dependency is measured in the photoluminescence measurement for the first p-type light absorption layer 10 The following formula (2)

K is preferably 1 <k <2.

  The value of k in the photoluminescence measurement represents the origin of light emission, and light emission having a k value within the above range is exciton light emission. Exciton luminescence is obtained from a thin film with very good crystallinity. Thin films with very good crystallinity have high carrier transport properties. Therefore, high conversion efficiency can be obtained by using, as the light absorption layer, a film from which photoluminescence emission having a k value within the above range can be obtained.

(Method for manufacturing solar cell)
In the present embodiment, first, the back electrode layer 8 is formed on the soda lime glass 6. The back electrode layer 8 is a metal layer usually made of Mo. Examples of the method for forming the back electrode layer 6 include sputtering of a Mo target.

  After forming the back electrode layer 8 on the soda lime glass 6, the first p-type light absorption layer 10 is formed on the back electrode layer 8. Examples of the method for forming the first p-type absorber layer 10 include a one-step simultaneous vacuum deposition method, a two-step vacuum deposition method, a solid phase selenization method, and a gas phase selenization method.

  The first p-type absorber layer 10 is preferably formed once such that the Ib group-VIb group composition is larger than 1.0, that is, the Ib-rich composition.

  For example, when the one-stage vacuum deposition method is used, it is preferable to set the group IIIb evaporation pressure (flux) to 7 times or less of the group Ib evaporation pressure (flux). If the value is larger than 7 times, the Ib-rich composition cannot be obtained, and the effect of the present invention is reduced.

  For example, when a two-stage vacuum vapor deposition method is used, the IIIb group element and the VIb group element are vapor-deposited simultaneously in the first stage. In the second stage, the Ib group element and the VIb group element are vapor-deposited at the same time.

For example, when a solid phase selenization method or a vapor phase selenization method is used, the precursor is Cu ₂ Se, Cu ₂ S, Ag ₂ Se, Ag ₂ S or other group Ib-VIb group element compound film or Cu. Group Ib elements including Ag, and Group IIIb-VIb including In ₂ Se ₃ , In ₂ S ₃ , Ga ₂ Se ₃ , Ga ₂ S ₃ , Al ₂ Se ₃ , Al ₂ S ₃ An element compound film or a group IIIb element film including In, Ga, and Al is formed. Thereafter, heat treatment is performed in an atmosphere containing solid Se, solid S, hydrogen selenide, or hydrogen sulfide to form the first p-type absorber layer 10. For the formation of the precursor, vacuum deposition, sputtering, electrodeposition, printing, or the like is used. The Ib-rich composition is adjusted by the ratio of the film thickness of the Ib group-VIb group element compound film or the Ib group element film and the IIIb group-VIb group element compound film or the IIIb group element film.

  It is preferable that the Ib group element / IIIb group element ratio of the first p-type absorber layer 10 produced by the above method once reaches the range of 1.1 to 1.6. Thereby, the effect of the present invention becomes remarkable. When the ratio is smaller than 1.1, the film has a relatively small carrier transport property and the effect of the present invention is small. When the ratio is larger than 1.6, the conductive group Ib-VI group compound, which usually precipitates only on the film surface, also precipitates at the crystal grain boundaries in the film, making it difficult to completely remove in the subsequent steps. There exists a tendency for the effect of invention to become small.

  After the first p-type absorber layer 10 is formed, it is preferable to remove excess group Ib-VIb group compounds. Examples of a method for removing the Ib group-VIb group compound which is a different phase include an etching treatment by immersion in an aqueous potassium cyanide solution, a method by electrochemical etching or a heat treatment in a forming gas atmosphere, and the like. Alternatively, a method may be used in which a group Ib group and a group VIb compound are formed by reacting and consuming with an excessive group Ib group-VIb group compound by co-deposition of group IIIb and group VIb. By these methods, different phases including conductive Ib-VIb group compounds such as CuxSe, CuxS, AgxSe, and AgxS can be removed from the first p-type light absorption layer 10, and the effect of the present invention is remarkable. It becomes.

  It is preferable that the Ib group / IIIb group ratio of the layer finally used as the first p-type absorber layer 10 after removing the heterogeneous phase by the above method is 1.0. By adopting this method, it is possible to form a layer having a high carrier transport property having a photoluminescence or cathodoluminescence spectrum having a narrow half-value width, which does not contain a group Ib-VIb compound which is a conductive heterogeneous phase. It becomes easy to obtain good conversion efficiency by using the layer for the first p-type light absorption layer 10 of the solar cell of the present invention.

  After forming the first p-type light absorption layer 10, the second light absorption layer 12 is formed on the first p-type light absorption layer 10. Examples of the method for forming the second light absorption layer 12 include the following methods.

  In the first method, the second light absorption layer 12 is formed on the first p-type light absorption layer 10 by vacuum deposition. As a specific example, a laminated body (hereinafter referred to as “substrate”) including soda lime glass 6, back electrode layer 8 and first p-type light absorption layer 10 is placed in a vapor deposition apparatus and evacuated. Thereafter, the group IIIb element and the group VIb element are simultaneously deposited while heating the substrate.

  In the first method, the second light absorption layer 12 is formed by a reaction between the group Ib element diffused from the first p-type light absorption layer 10 in the surface direction and the deposited group IIIb element and group VIb element. .

  In the first method, the composition and film thickness can be appropriately controlled within the above ranges by adjusting the evaporation amount (flux) of each element supplied into the vapor deposition apparatus.

  In the first method, the temperature of the substrate is preferably 100 to 550 ° C. When the temperature of the substrate is too low, the reaction between the IIIb group element and the VIb group element hardly occurs, and the desired composition and film thickness of the second light absorption layer 12 tend to be difficult to obtain. On the other hand, when the temperature of the substrate is too high, the substrate tends to be softened and deformed or dissolved, and the film forming rate tends to be remarkably reduced. These tendencies can be suppressed by setting the temperature of the substrate within the above range.

  In the first method, the substrate temperature is more preferably 250 to 350 ° C. When the second light absorption layer 12 is formed at a temperature below this range, a compound is likely to be generated only between the group IIIb element and the group VIb element, which tends to hinder light absorption and carrier transport and deteriorate characteristics. is there. In addition, the crystallinity of the second light absorption layer 12 is deteriorated and good characteristics tend not to be obtained. When the second light absorption layer 12 is formed at a temperature higher than this range, excessive diffusion of the Ib group element from the first p-type light absorption layer 10 in the surface direction tends to occur, and the first p-type light absorption. The Ib group / IIIb group element ratio of the layer 10 tends to decrease and the Ib group / IIIb group ratio of the second light absorption layer 12 tends to increase, making composition control relatively difficult.

  In the first method, when the substrate temperature is set to 350 to 550 ° C., it is preferable to deposit the Ib group element in addition to the IIIb group element and the VIb group element. Thereby, excessive diffusion of the Ib group element from the first p-type light absorption layer 10 to the second light absorption layer 12 can be suppressed. When excessive diffusion of the Ib group element from the first p-type light absorption layer 10 in the surface direction occurs, the Ib group / IIIb group ratio of the first p-type light absorption layer 10 tends to decrease. At the same time, the Ib group / IIIb group element ratio of the second light absorption layer 12 tends to increase, making composition control relatively difficult. Further, when excessive diffusion of the group Ib element from the first p-type light absorption layer 10 to the film surface direction, that is, the second light absorption layer 12, occurs, the photo obtained from the first p-type light absorption layer There is a tendency that the full width at half maximum of the luminescence or cathodoluminescence spectrum is increased. As a result, carrier transport characteristics are likely to deteriorate. This tendency can be suppressed by adding an Ib group element during vapor deposition for forming the second light absorption layer 12.

  The group IIIb element used in the first method is preferably the same as the group IIIb element contained in the first p-type absorber layer 10. When the Ib group element is also used in the first method, it is preferably the same as the Ib group element contained in the first p-type absorber layer 10. Thereby, the effect of the present invention becomes remarkable.

  In the second method, the second light absorption layer 12 is formed on the first p-type light absorption layer 10 by sputtering. As a specific example, a stack (hereinafter referred to as “substrate”) including soda lime glass 6, back electrode layer 8 and first p-type light absorption layer 10, and a sputtering target composed of a IIIb group-VIb group compound are provided. Install inside and evacuate. Thereafter, the second light absorption layer 12 is formed by sputtering the target while heating the substrate.

  In the second method, the composition can be appropriately controlled within the above range by adjusting the composition of each element of the sputtering target installed in the sputtering apparatus.

  In the second method, the temperature of the substrate is preferably 100 to 550 ° C. When the temperature of the substrate is too low, the reaction between the IIIb group element and the VIb group element hardly occurs, and the desired composition and film thickness of the second light absorption layer 12 tend to be difficult to obtain. On the other hand, when the temperature of the substrate is too high, the substrate tends to be softened and deformed or dissolved, and the film forming rate tends to be remarkably reduced. These tendencies can be suppressed by setting the temperature of the substrate within the above range.

  In the second method, the substrate temperature is more preferably 250 to 350 ° C. When the second light absorption layer 12 is formed at a temperature below this range, a compound is likely to be generated only between the group IIIb element and the group VIb element, which tends to hinder light absorption and carrier transport and deteriorate characteristics. is there. In addition, the crystallinity of the second light absorption layer 12 is deteriorated and good characteristics tend not to be obtained. When the second light absorption layer 12 is formed at a temperature higher than this range, the first p-type light is absorbed when excessive diffusion of the group Ib element from the first p-type light absorption layer 10 toward the surface occurs. The Ib group / IIIb group element ratio of the absorption layer 10 tends to decrease, and the Ib group / IIIb group element ratio of the second light absorption layer 12 tends to increase, making composition control relatively difficult.

  In the second method, when the substrate temperature is set to 350 to 550 ° C., it is preferable to use a sputtering target containing a group Ib element in addition to a group IIIb element and a group VIb element. Thereby, excessive diffusion of the Ib group element from the first p-type light absorption layer 10 to the second light absorption layer 12 can be suppressed. When excessive diffusion of the group Ib element from the first p-type light absorption layer 10 occurs, the half width of the photoluminescence or cathodoluminescence spectrum obtained from the first p-type light absorption layer tends to increase. As a result, carrier transport characteristics are likely to deteriorate. This tendency can be suppressed by adding a group Ib element to the target.

  In the second method, the group IIIb element contained in the sputtering target is preferably the same as the group IIIb element contained in the first p-type absorber layer 10. In the second method, when the lb group element is added to the sputtering target, the lb group element is preferably the same as the lb group element contained in the first p-type absorber layer 10. Thereby, the effect of the present invention becomes remarkable.

  In the third method, a layer containing a group IIIb element and a group VIb element (hereinafter referred to as “surface precursor layer”) is formed by a vacuum deposition method or a sputtering method using an apparatus having the same configuration as the first method or the second method. The second light absorption layer 12 is formed by performing a heat treatment after the formation.

  In the third method, the heat treatment is preferably performed in an atmosphere containing a solid VIb group element, hydrogen selenide, or hydrogen sulfide. When the first p-type absorber layer 10 is heated, the VIb group element tends to be desorbed and changed from p-type to n-type. This tendency can be suppressed by performing the heat treatment in an atmosphere containing a solid VIb group element, hydrogen selenide, or hydrogen sulfide.

  In the third method, the temperature during film formation by vacuum deposition or sputtering is preferably 200 ° C. or lower. This makes it easier to control the thickness of the second light absorption layer.

  In the third method, the heat treatment temperature is preferably 250 to 550 ° C. Furthermore, it is more preferable to set it as 250-350 degreeC. If the heat treatment temperature is too low, the surface precursor layer tends to remain. If the heat treatment temperature is too high, the substrate tends to soften and deform or dissolve. Further, even at 350 to 550 ° C., which is a temperature that does not soften or dissolve, excessive diffusion of the Ib group element from the first p-type light absorption layer 10 toward the surface tends to occur. The Ib group / IIIb group element ratio of the first p-type light absorption layer 10 tends to decrease, and the Ib group / IIIb group element ratio of the second light absorption layer 12 tends to increase. Relatively difficult. When excessive diffusion of the group Ib element from the first p-type light absorption layer 10 occurs, the half width of the photoluminescence or cathodoluminescence spectrum obtained from the first p-type light absorption layer tends to increase. As a result, carrier transport characteristics are likely to deteriorate. These tendencies can be suppressed by setting the temperature of the substrate within the above range.

  In the third method, when the heat treatment temperature is 350 to 550 ° C., it is preferable to include an Ib group element in addition to the IIIb group element and the VIb group element at the time of film formation by a vacuum deposition method or a sputtering method. Thereby, excessive diffusion of the Ib group element from the first p-type light absorption layer 10 to the second light absorption layer 12 can be suppressed. When excessive diffusion of the group Ib element from the first p-type light absorption layer 10 occurs, the half width of the photoluminescence or cathodoluminescence spectrum obtained from the first p-type light absorption layer tends to increase. As a result, carrier transport characteristics are likely to deteriorate. This tendency can be suppressed by adding a group Ib element to the target.

  In the third method, the group IIIb element used in the vacuum deposition method or the group IIIb element contained in the sputtering target is preferably the same as the group IIIb element contained in the first p-type absorber layer 10. In the third method, when adding a group Ib element to a vapor deposition source or sputtering target used for vacuum deposition, the group Ib element is also preferably the same as the group Ib element contained in the first p-type light absorption layer 10. . Thereby, the effect of the present invention becomes remarkable.

  In the present embodiment, the formation conditions are set so that the ratio of the Ib group element / IIIb group element contained in the second light absorption layer 12 is 0.1 or more and less than 1.0.

  In the case of the first method, the composition of the second light absorption layer 12 can be appropriately controlled within the above range by adjusting the temperature of the substrate and the flux amount of each element.

  In the case of the second method, the composition of the second light absorption layer 12 can be appropriately controlled within the above range by adjusting the temperature of the substrate and the composition ratio of each element included in the target.

  Also in the case of the third method, the composition of the second light absorption layer 12 can be controlled within the above range by the same method as the first method and the second method.

  In the present embodiment, it is preferable to set the formation conditions so that the thickness of the second light absorption layer 12 is 1 nm or more and 100 nm or less.

  In the case of the first method, the thickness of the second light absorption layer 12 can be appropriately controlled within the above range by adjusting the substrate temperature, the flux amount of each element, and the film formation time.

  In the case of the second method, the thickness of the second light absorption layer 12 can be appropriately controlled within the above range by adjusting the substrate temperature, the distance between the substrate and the target, the sputtering power, and the film formation time. It becomes.

  Also in the case of the third method, the thickness of the second light absorption layer 12 can be controlled within the above range by the same method as the first method and the second method. In addition, the thickness of the second light absorption layer 12 can be appropriately controlled within the above range by adjusting the heat treatment temperature and the heat treatment time.

After the formation of the second light absorption layer 12, the n-type buffer layer 14 is formed on the second light absorption layer 12. Examples of the n-type buffer layer 14 include a CdS layer, a Zn (S, O, OH) layer, a ZnMgO layer, or a Zn (O _x , S _1-x ) layer (x is a positive real number less than 1). It is done. The CdS layer and the Zn (S, O, OH) layer can be formed by a solution growth method (Chemical Bath Deposition). The ZnMgO layer can be formed by chemical vapor deposition such as MOCVD (Metal Organic Chemical Vapor Deposition) or sputtering. The Zn (O _x , S _1-x ) layer can be formed by an ALD method (Atomic layer deposition) or the like.

  After the formation of the n-type buffer layer 14, the semi-insulating layer 16 is formed on the n-type buffer layer 14, the window layer 18 is formed on the semi-insulating layer 16, and the upper electrode 20 is formed on the window layer 18.

  Examples of the semi-insulating layer 16 include a ZnO layer and a ZnMgO layer.

  Examples of the window layer 18 include ZnO: Al, ZnO: B, ZnO: Ga, and ITO.

  The semi-insulating layer 16 and the window layer 18 can be formed by chemical vapor deposition such as MOCVD (Metal Organic Chemical Vapor Deposition) or sputtering.

The upper electrode 20 is made of a metal such as Al or Ni. The upper electrode 20 can be formed by resistance heating vapor deposition, electron beam vapor deposition, or sputtering. Thereby, the thin film type solar cell 4 is obtained. An antireflection layer may be formed on the window layer 18. The antireflection layer, for example _{MgF 2,} TiO _2, SiO 2 and the like. The window layer 18 can be formed by resistance heating vapor deposition, electron beam vapor deposition, sputtering, or the like.

  As mentioned above, although one suitable embodiment of the present invention was described in detail, the present invention is not limited to the above-mentioned embodiment. For example, the first p-type light absorption layer 10 and the second light absorption layer 12 are formed by printing, electrodeposition, chemical solution growth, gas phase selenization, gas phase sulfidation, solid phase selenization, solid phase You may form by the sulfurization method or the method which combined them. The solar cell 4 according to the above embodiment can be manufactured.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
After washing and drying soda lime glass having a length of 10 cm, a width of 10 cm, and a thickness of 1 mm, a film-like back electrode composed of Mo alone was formed on the soda lime glass by a DC sputtering method. The film thickness of the back electrode was 1 μm.

  In Example 1, “substrate” means an object to be deposited or an object to be measured in each step.

  Subsequently, the first p-type absorber layer was formed by a physical vapor deposition (physical vapor deposition, hereinafter referred to as PVD) apparatus by a vacuum vapor deposition method. The film composition was adjusted by measuring the relationship between the flux ratio of each raw material element and the composition contained in the obtained film before film formation in each step in the PVD apparatus. The flux of each element was appropriately changed by adjusting the temperature of each K cell. In the first p-type absorber layer forming step of Example 1, the flux of each element was set so that the lb group / IIIb group composition ratio immediately after film formation was 1.01.

The back electrode formed on the soda lime glass was placed in the chamber of the PVD apparatus, and the inside of the chamber was evacuated. The ultimate pressure in the vacuum apparatus was 1.0 × 10 ⁻⁸ torr.

  Then, after the substrate was heated to 540 ° C. and the temperature was stabilized, the shutter of each Cu, In, and Se K cell was opened to deposit Cu, In, and Se on the substrate. When a layer having a thickness of about 2 μm was formed on the substrate by this deposition, the shutters of the Cu and In K cells were closed. Then, after cooling the substrate to 200 ° C., the shutter of the Se K cell was closed, and the film formation of the first p-type semiconductor layer was completed.

  Composition analysis of each element included in the first p-type light absorption layer was performed by energy dispersive X-ray spectroscopy (EDX). The Cu / In composition ratio of the first p-type light absorption layer immediately after film formation was 1.01.

  After the formation of the first p-type light absorption layer, the substrate is immersed in an aqueous potassium cyanide solution (10 wt%) for 5 minutes to remove the Ib group-VIb group compound which is a different phase contained in the first p-type light absorption layer. It was.

  The composition analysis of each element included in the first p-type light absorption layer after the heterogeneous phase removal treatment was performed by an energy dispersive X-ray spectroscopy (EDX) method. The Cu / In composition ratio of the p-type absorber layer after the heterogeneous removal treatment was 0.98.

  After the heterogeneous phase removal treatment of the first p-type light absorption layer, a second light absorption layer was formed on the first p-type light absorption layer by vacuum deposition. Hereinafter, the formation of the second light absorption layer will be described.

The substrate was placed in the chamber of the PVD apparatus, and the inside of the chamber was evacuated. The ultimate pressure in the vacuum apparatus was 1.0 × 10 ⁻⁸ torr.

Then, after the substrate was heated to 300 ° C. and the temperature was stabilized, the shutters of the K cells of In and Se were opened, and In and Se were deposited on the substrate. When a layer having a thickness of about 20 nm was formed on the substrate by this vapor deposition, the shutter of the In K cell was closed.

  In this step, the lb group element diffused from the first p-type light absorption layer toward the film surface and the IIIb group element and the VIb group element from the surface by the main vapor deposition step are supplied from the Ib group, IIIb group, and VIb group compounds. A second light absorption layer was formed.

  Then, after cooling the substrate to 200 ° C., the shutter of the Se K cell was closed, and the film formation of the second light absorption layer was completed.

  The composition analysis of each element included in the second light absorption layer was performed by Auger Electron Spectroscopy (AES). The Cu / In composition ratio of the second light absorption layer was 0.35.

  After the formation of the second light absorption layer, a CdS buffer layer, which is an n-type semiconductor layer having a thickness of 50 nm, was formed on the second light absorption layer by a chemical solution deposition (CBD) method.

  After the formation of the n-type semiconductor layer, an i-ZnO layer (semi-insulating layer) having a thickness of 50 nm was formed on the n-type semiconductor layer. Subsequently, a ZnO: Al layer (window layer) having a thickness of 0.5 μm was formed on the i-ZnO layer in the same chamber.

After the window layer was formed, photoluminescence measurement of the first p-type light absorption layer was performed. An Ar ion laser having a wavelength of 514.5 nm was used as an excitation light source used for measurement, and the substrate was cooled to 10 K (Kelvin) by a cryostat during measurement. The excitation light intensity was changed from 1 mW / cm ² to 100 mW / cm ² and the dependence of the photoluminescence intensity on the excitation light intensity was measured.

In the photoluminescence spectrum obtained at the time of measuring 10 mW / cm ² , the half width of light emission having the narrowest half width was 15 meV.

When the relationship between the photoluminescence intensity I _PL and the excitation light intensity I _ex ^k obtained by the measurement was expressed by the following formula (2), the value of k was 1.03.

  Further, a part of the substrate was cut, and the cathodoluminescence measurement of the first p-type absorber layer was performed from the fracture surface. The measurement was performed at 10 K (Kelvin) as in the case of photoluminescence. In the cathodoluminescence spectrum obtained by the measurement, the half-value width of light emission with the narrowest half-value width was 15 meV.

  After the window layer was formed, an upper electrode composed of Ni having a thickness of 50 nm and Al having a thickness of 1 μm thereon was formed on the ZnO: Al layer. The i-ZnO layer, the ZnO: Al layer, and the upper electrode were each formed by sputtering. Thereby, the thin film type solar cell of Example 1 was obtained.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group of the first p-type light absorption layer after the different phase removal treatment / IIIb group composition ratio, the half-width value of the narrowest half-value emission in the photoluminescence spectrum and cathodoluminescence spectrum of the first p-type light absorption layer, and the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity Table 1 shows the foreign phase removal method.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 2 shows the manufacturing method and film forming temperature.

(Comparative Example 1)
In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio of the first p-type absorber layer immediately after the deposition was 1.25. The second light absorbing layer was not provided.

  Except for the above, a solar cell of Comparative Example 1 was produced in the same manner as in Example 1.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group of the first p-type light absorption layer after the different phase removal treatment / IIIb group composition ratio, the half-width value of the narrowest half-value emission in the photoluminescence spectrum and cathodoluminescence spectrum of the first p-type light absorption layer, and the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity Table 1 shows the foreign phase removal method.

(Comparative Example 2)
In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio of the first p-type absorber layer immediately after the film formation was 0.90. In addition, the foreign phase removal treatment was not performed.

  Except for the above, a solar cell of Comparative Example 2 was produced in the same manner as in Example 1.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group of the first p-type light absorption layer after the different phase removal treatment / IIIb group composition ratio, the half-width value of the narrowest half-value emission in the photoluminescence spectrum and cathodoluminescence spectrum of the first p-type light absorption layer, and the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity Table 1 shows the foreign phase removal method.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 2 shows the manufacturing method and film forming temperature.

(Examples 2 to 6)
In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio of the first p-type absorber layer immediately after the film formation was the value shown in Table 1.

  Except for the above matters, solar cells of Examples 2 to 6 were produced in the same manner as in Example 1.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group of the first p-type light absorption layer after the different phase removal treatment / IIIb group composition ratio, the half-width value of the narrowest half-value emission in the photoluminescence spectrum and cathodoluminescence spectrum of the first p-type light absorption layer, and the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity Table 1 shows the foreign phase removal method.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 2 shows the manufacturing method and film forming temperature.

(Examples 7 to 11, Comparative Example 3)
In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio immediately after the film formation was a value shown in Table 3.

  In the second light absorption layer deposition step, the deposition temperature was set to the values shown in Table 4.

  Except for the above matters, solar cells of Examples 7 to 11 and Comparative Example 3 were produced in the same manner as in Example 1.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group of the first p-type light absorption layer after the different phase removal treatment / IIIb group composition ratio, the half-width value of the narrowest half-value emission in the photoluminescence spectrum and cathodoluminescence spectrum of the first p-type light absorption layer, and the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity Table 3 shows the foreign phase removal method.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 4 shows the manufacturing method and the film formation temperature.

(Examples 12 to 14, Comparative Example 4)
In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio immediately after the film formation was a value shown in Table 3.

  After the heterogeneous phase removal treatment of the first p-type light absorption layer, a second light absorption layer was formed on the first p-type light absorption layer by vacuum deposition.

The substrate was placed in the chamber of the PVD apparatus, and the inside of the chamber was evacuated. The ultimate pressure in the vacuum apparatus was 1.0 × 10 ⁻⁸ torr.

  The flux of each element was set in advance so that the Ib group / IIIb group composition ratio of the second light absorption layer became the value shown in Table 4.

  Then, after the substrate was heated to the temperature shown in Table 4 and the temperature was stabilized, the shutter of each K cell of Cu, In, and Se was opened, and Cu, In, and Se were deposited on the substrate. When a layer having a thickness of about 20 nm was formed on the substrate by this deposition, the shutters of the Cu and In K cells were closed.

  Then, after cooling the substrate to 200 ° C., the shutter of the Se K cell was closed, and the film formation of the second light absorption layer was completed.

  Except for the above items, solar cells of Examples 12 to 14 and Comparative Example 4 were produced in the same manner as in Example 1.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group of the first p-type light absorption layer after the different phase removal treatment / IIIb group composition ratio, the half-width value of the narrowest half-value emission in the photoluminescence spectrum and cathodoluminescence spectrum of the first p-type light absorption layer, and the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity Table 3 shows the foreign phase removal method.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second layer, production method of second light absorption layer Table 4 shows the film formation temperature.

(Examples 15 to 21)
The materials shown in Table 5 were used as the first p-type light absorption layer.

  In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio immediately after the film formation was a value shown in Table 5.

  When the first p-type light absorbing layer contains a plurality of group IIIb elements, the flux was set so that the composition thereof had the values shown in Table 5.

  After the substrate was heated to 540 ° C., the shutters of the elements of the first p-type light absorption layer material shown in Table 5 were each opened and deposited on the substrate.

  Except for the above matters, solar cells of Examples 15 to 21 were produced in the same manner as in Example 1.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group of the first p-type light absorption layer after the different phase removal treatment / IIIb group composition ratio, the half-width value of the narrowest half-width emission in the photoluminescence spectrum and cathodoluminescence spectrum of the first p-type light absorption layer, and the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity Table 5 shows the foreign phase removal method.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 6 shows the manufacturing method and film forming temperature.

(Comparative Examples 5-11)
The materials shown in Table 5 were used for the p-type light absorption layer.

  The second light absorption layer was not provided.

  Except for the above matters, solar cells of Comparative Examples 5 to 11 were produced in the same manner as in Examples 15 to 21.

  Compound used for p-type light absorption layer, Ib group / IIIb group composition ratio of p-type light absorption layer immediately after film formation, Ib group / IIIb group composition ratio after heterophasic removal treatment, photoluminescence spectrum of p-type light absorption layer Table 5 shows the half-value width of the light emission with the narrowest half-value width in the cathodoluminescence spectrum, the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity, and the method for removing the different phases.

(Example 22)
The materials shown in Table 7 were used as the first p-type light absorption layer.

  In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio immediately after the film formation was a value shown in Table 7.

  Except for the above, a solar cell of Example 22 was produced in the same manner as in Example 1.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group of the first p-type light absorption layer after the different phase removal treatment / IIIb group composition ratio, the half-width value of the narrowest half-value emission in the photoluminescence spectrum and cathodoluminescence spectrum of the first p-type light absorption layer, and the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity Table 7 shows the foreign phase removal method.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 8 shows the manufacturing method and film forming temperature.

(Example 23)
The materials shown in Table 7 were used as the first p-type light absorption layer.

  In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio immediately after the film formation was a value shown in Table 7.

  After the heterogeneous phase removal treatment of the first p-type light absorption layer, a second light absorption layer was formed on the p-type light absorption layer by vacuum deposition.

The substrate was placed in the chamber of the PVD apparatus, and the inside of the chamber was evacuated. The ultimate pressure in the vacuum apparatus was 1.0 × 10 ⁻⁸ torr.

  Then, after the substrate was heated to 300 ° C. and the temperature was stabilized, the shutters of the Ga and Se K cells were opened to deposit Ga and Se on the substrate. When a layer having a thickness of about 20 nm was formed on the substrate by this vapor deposition, the shutter of the Ga K cell was closed.

  In this step, a second light absorption layer was formed by supplying a group Ib element diffusing from the first p-type light absorption layer toward the film surface and a group IIIb element and a group VIb element from the surface in this vapor deposition step.

  Then, after cooling the substrate to 200 ° C., the shutter of the Se K cell was closed, and the film formation of the second light absorption layer was completed.

  Except for the above, a solar cell of Example 23 was produced in the same manner as in Example 1.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group of the first p-type light absorption layer after the different phase removal treatment / IIIb group composition ratio, the half-width value of the narrowest half-value emission in the photoluminescence spectrum and cathodoluminescence spectrum of the first p-type light absorption layer, and the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity Table 7 shows the foreign phase removal method.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 8 shows the manufacturing method and film forming temperature.

(Example 24)
The materials shown in Table 7 were used as the first p-type light absorption layer.

  After the heterogeneous phase removal treatment of the first p-type light absorption layer, a second light absorption layer was formed on the p-type light absorption layer by vacuum deposition.

After the heterogeneous phase removal treatment of the first p-type absorber layer, the substrate was placed in the chamber of the PVD apparatus and the inside of the chamber was evacuated. The ultimate pressure in the vacuum apparatus was 1.0 × 10 ⁻⁸ torr.

  Then, after the substrate was heated to 300 ° C. and the temperature was stabilized, the shutters of the Cu, In, and Se K cells were opened, and Cu, In, and Se were deposited on the substrate. When a layer having a thickness of about 20 nm was formed on the substrate by this vapor deposition, the shutter of the Cu and In K cells was closed.

  In this step, a second light absorption layer was formed by supplying a group Ib element diffusing from the first p-type light absorption layer toward the film surface and a group IIIb element and a group VIb element from the surface in this vapor deposition step.

  Then, after cooling the substrate to 200 ° C., the shutter of the Se K cell was closed, and the film formation of the second light absorption layer was completed.

  A solar cell of Example 24 was made in the same manner as in Example 15 except for the above items.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group of the first p-type light absorption layer after the different phase removal treatment / IIIb group composition ratio, the half-width value of the narrowest half-value emission in the photoluminescence spectrum and cathodoluminescence spectrum of the first p-type light absorption layer, and the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity Table 7 shows the foreign phase removal method.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 8 shows the manufacturing method and film forming temperature.

(Example 25)
The materials shown in Table 7 were used as the first p-type light absorption layer.

  Except for the above, a solar cell of Example 25 was produced in the same manner as in Example 15.

  Compound used for first p-type light absorption layer, Ib group / IIIb group composition ratio of first p-type light absorption layer immediately after film formation, Ib group / IIIb group composition ratio after heterophase removal treatment, p-type light Table 7 shows the half-width value of the light emission with the narrowest half-value width in the photoluminescence spectrum and the cathodoluminescence spectrum of the absorption layer, the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity, and the method for removing the different phases.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 8 shows the manufacturing method and film forming temperature.

(Example 26)
The materials shown in Table 7 were used as the first p-type light absorption layer. The flux of each element was set so as to have the composition shown in Table 7. In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio immediately after the film formation was a value shown in Table 7.

  After the heterogeneous phase removal treatment of the first p-type light absorption layer, a second light absorption layer was formed on the p-type light absorption layer by vacuum deposition.

After the heterogeneous phase removal treatment of the first p-type absorber layer, the substrate was placed in the chamber of the PVD apparatus and the inside of the chamber was evacuated. The ultimate pressure in the vacuum apparatus was 1.0 × 10 ⁻⁸ torr.

The temperature of each K cell was set so that the ratio of each flux of In and Ga was the same as that in the first p-type absorber layer film forming step. Thereafter, the substrate was heated to the temperature shown in Table 8 and the temperature was stabilized. Then, the shutter of each K cell of In, Ga, and Se was opened, and In, Ga, and Se were deposited on the substrate. When a layer having a thickness of about 20 nm was formed on the substrate by this vapor deposition, the shutters of the In and Ga K cells were closed.
Then, after cooling the substrate to 200 ° C., the shutter of the Se K cell was closed, and the film formation of the second light absorption layer was completed.

  Except for the above, a solar cell of Example 26 was produced in the same manner as in Example 15.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group of the first p-type light absorption layer after the different phase removal treatment / IIIb group composition ratio, the half-width value of the narrowest half-value emission in the photoluminescence spectrum and cathodoluminescence spectrum of the first p-type light absorption layer, and the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity Table 7 shows the foreign phase removal method.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 8 shows the manufacturing method and film forming temperature.

(Example 27)
The ratio of each flux of In and Ga in the second light absorption layer forming step was set so that the composition ratio Ga / (In + Ga) in the second light absorption layer was 0.3.

  A solar cell of Example 27 was made in the same manner as in Example 26 except for the above items.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group of the first p-type light absorption layer after the different phase removal treatment / IIIb group composition ratio, the half-width value of the narrowest half-value emission in the photoluminescence spectrum and cathodoluminescence spectrum of the first p-type light absorption layer, and the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity Table 7 shows the foreign phase removal method.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 8 shows the manufacturing method and film forming temperature.

(Examples 28 to 29)
The materials shown in Table 9 were used as the first p-type light absorption layer. In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio immediately after the film formation was a value shown in Table 9. The flux was set so that the ratio of the plurality of group IIIb elements was the value shown in Table 9.

  Except for the above items, solar cells of Examples 28 to 29 were produced in the same manner as in Example 26.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group / IIIb group composition ratio after the heterophase removal treatment, Table 9 shows the half-value width of the light emission with the narrowest half-value width in the photoluminescence spectrum and the cathodoluminescence spectrum of the p-type light absorption layer, and the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity and the method for removing the different phases. Show.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 10 shows the manufacturing method and the film formation temperature.

(Examples 30 to 36)
The material shown in Table 11 was used as the first p-type light absorption layer. In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio immediately after the film formation was a value shown in Table 11.

  After the heterogeneous phase removal treatment of the first p-type light absorption layer, a second light absorption layer was formed on the first p-type light absorption layer by vacuum deposition.

The substrate was placed in the chamber of the PVD apparatus, and the inside of the chamber was evacuated. The ultimate pressure in the vacuum apparatus was 1.0 × 10 ⁻⁸ torr.

The temperature of each K cell was set so that the ratio of each flux of In and Ga was the same as that in the first p-type absorber layer film forming step. Then, after the substrate was heated to the temperature shown in Table 12 and the temperature was stabilized, the shutter of each K cell of In, Ga, and Se was opened, and In, Ga, and Se were deposited on the substrate. When a layer having the thickness shown in Table 12 was formed on the substrate by this vapor deposition, the shutters of the In and Ga K cells were closed.
Then, after cooling the substrate to 200 ° C., the shutter of the Se K cell was closed, and the film formation of the second light absorption layer was completed.

  Except for the above matters, solar cells of Examples 30 to 36 were produced in the same manner as in Example 26.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group / IIIb group composition ratio after the heterophase removal treatment, Table 11 shows the half-width value of the light emission with the narrowest half-value width in the photoluminescence spectrum and the cathodoluminescence spectrum of the p-type light absorption layer, the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity, and the heterophase removal method. Show.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 12 shows the production method and film formation temperature.

(Example 37)
The materials shown in Table 13 were used as the first p-type light absorption layer. In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio immediately after the film formation was a value shown in Table 13.

  After the formation of the first p-type light absorption layer, the second phase light absorption layer was formed on the first p-type light absorption layer without performing the different phase removal treatment.

  A solar cell of Example 37 was made in the same manner as in Example 26 except for the above items.

  Compound used for first p-type light absorption layer, Ib group / IIIb group composition ratio of first p-type light absorption layer immediately after film formation, photoluminescence spectrum and cathodoluminescence spectrum of first p-type light absorption layer Table 13 shows the value of the half-value width of the light emission with the narrowest half-value width in k, the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity, and the heterophase removal method.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 14 shows the manufacturing method and film forming temperature.

(Example 38)
The materials shown in Table 13 were used as the first p-type light absorption layer. In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio immediately after the film formation was a value shown in Table 13.

  A solar cell of Example 38 was made in the same manner as in Example 26 except for the above items.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group / IIIb group composition ratio after the heterophase removal treatment, Table 13 shows the half-width value of the light emission with the narrowest half-value width in the photoluminescence spectrum and the cathodoluminescence spectrum of the p-type light absorption layer, and the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity and the method for removing the different phases. Show.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 14 shows the manufacturing method and film forming temperature.

(Example 39)
The materials shown in Table 13 were used as the first p-type light absorption layer. In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio immediately after the film formation was a value shown in Table 13.

After the first p-type absorber layer was formed, the substrate was placed in a rapid heating heat treatment furnace. Heating treatment was performed while forming gas (H ₂ 95%, N ₂ 5%) was supplied into the furnace at a flow rate of 200 sccm. The temperature was 400 ° C., the temperature increase rate was 400 ° C./min, and the heat treatment time was 30 s. After the heat treatment, the substrate was cooled to 50 ° C. at a rate of 50 ° C./min, and the substrate was taken out. By this treatment, the Ib group-VIb group compound, which is a different phase contained in the first p-type absorber layer, was removed.

  A solar cell of Example 39 was made by the same method as that in Example 26 except for the above items.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group / IIIb group composition ratio after the heterophase removal treatment, Table 13 shows the half-width value of the light emission with the narrowest half-value width in the photoluminescence spectrum and the cathodoluminescence spectrum of the p-type light absorption layer, and the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity and the method for removing the different phases. Show.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 14 shows the manufacturing method and film forming temperature.

(Example 40)
The materials shown in Table 13 were used as the first p-type light absorption layer. In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio immediately after the film formation was a value shown in Table 13.

After forming the first p-type absorber layer, the substrate was placed in an electrolytic cell equipped with a three-electrode cell. The Pt plate was the counter electrode, the saturated calomel electrode was the reference electrode, and the Mo back electrode exposed on the substrate was the working electrode. The electrolytic bath was filled with 0.1 M H ₂ SO ₄ solution (pH = 1.2), and electrochemical etching was performed by changing the potential from −0.5 V to +0.5 V at a scan rate of 10 mV / s. By this treatment, the Ib group-VIb group compound, which is a different phase contained in the first p-type absorber layer, was removed.

  A solar cell of Example 40 was made in the same manner as in Example 26 except for the above items.

  Compound used for first p-type light absorption layer, Ib group / IIIb group composition ratio of first p-type light absorption layer immediately after film formation, Ib group / IIIb group composition ratio after heterophase removal treatment, p-type light Table 13 shows the half-width value of the light emission with the narrowest half-value width in the photoluminescence spectrum and the cathodoluminescence spectrum of the absorption layer, the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity, and the method for removing the different phases.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 14 shows the manufacturing method and film forming temperature.

(Example 41)
The materials shown in Table 13 were used as the first p-type light absorption layer. In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio immediately after the film formation was a value shown in Table 13.

  After the first p-type absorber layer was formed, the substrate was left as it was in the vacuum chamber of the same PVD apparatus, and the substrate temperature was lowered to 300 degrees. The temperature of each K cell was set so that the ratio of each flux of In and Ga was the same as that in the first p-type absorber layer film forming step. Then, the shutter of each K cell of In, Ga, and Se was opened, and In, Ga, and Se were vapor-deposited on the board | substrate. By this vapor deposition, the CuxSe phase, which is a different phase present in the first p-type light absorption layer, was reacted with In and Ga to remove the different phase. When the heterogeneous phase disappeared, the shutters of the In and Ga K cells were closed. The presence of the foreign phase was monitored by measuring the surface roughness with a laser beam.

  After the heterogeneous phase removal step, the second light absorption layer was continuously formed in the PVD apparatus.

  A solar cell of Example 41 was made in the same manner as in Example 26 except for the above items.

  Compound used for first p-type light absorption layer, Ib group / IIIb group composition ratio of first p-type light absorption layer immediately after film formation, Ib group / IIIb group composition ratio after heterophase removal treatment, p-type light Table 13 shows the half-width value of the light emission with the narrowest half-value width in the photoluminescence spectrum and the cathodoluminescence spectrum of the absorption layer, the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity, and the method for removing the different phases.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 14 shows the manufacturing method and film forming temperature.

(Example 42)
The materials shown in Table 15 were used as the first p-type light absorption layer. In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio immediately after the film formation was a value shown in Table 15.

  A solar cell of Example 42 was made in the same manner as in Example 26 except for the above items.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group of the first p-type light absorption layer after the different phase removal treatment / IIIb group composition ratio, the half-width value of the narrowest half-value emission in the photoluminescence spectrum and cathodoluminescence spectrum of the first p-type light absorption layer, and the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity Table 15 shows the foreign phase removal method.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 16 shows the manufacturing method and the film formation temperature.

(Example 43)
The materials shown in Table 15 were used as the first p-type light absorption layer. In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio immediately after the film formation was a value shown in Table 15.

  After the formation of the first p-type light absorption layer, the substrate is immersed in an aqueous potassium cyanide solution (10 wt%) for 5 minutes to remove the Ib group-VIb group compound which is a different phase contained in the first p-type light absorption layer. It was.

  Thereafter, the substrate on which the first p-type light absorption layer was formed was placed in a sputtering apparatus, and the second light absorption layer was formed by a sputtering method.

  Details of the formation of the second light absorption layer by sputtering will be described below.

A substrate was placed in the sputtering apparatus, and the inside of the apparatus was evacuated. The ultimate pressure was 1.0 × 10 ⁻⁶ torr. After deaeration, the substrate was heated to 300 ° C. After that, while continuing to supply Ar gas into the chamber, a target composed of (In _0.5 Ga _0.5 ) ₂ Se ₃ was sputtered in the chamber to form a film on a substrate placed oppositely. During film formation, the flow rate of Ar gas was set so that the pressure in the chamber was 1 Pa. A second light absorption layer was formed by supplying the Ib group element diffusing from the p-type light absorption layer toward the film surface and (In _0.5 Ga _0.5 ) ₂ Se ₃ by this sputtering process. Sputtering was terminated when the thickness of the second light absorption layer reached 20 nm. By this step, a second light absorption layer was formed.

  Except for the above, a solar cell of Example 43 was produced in the same manner as in Example 26.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group / IIIb group composition ratio after the heterophase removal treatment, Table 15 shows the half-value width of the light emission with the narrowest half-value width in the photoluminescence spectrum and the cathodoluminescence spectrum of the p-type light absorption layer, and the value of k in the measurement of the excitation light intensity dependence of the photoluminescence intensity, and the method for removing the different phases. Show.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 16 shows the manufacturing method and the film formation temperature.

(Comparative Example 12)
The first p-type absorber layer was formed by sputtering and subsequent heat treatment. Details are shown below.

  The substrate on which the back electrode was formed was placed in a sputtering apparatus, and a precursor layer was formed by a sputtering method. Thereafter, the substrate was placed in an annealing furnace, and a first p-type semiconductor layer was formed by heat treatment. Details of the first p-type semiconductor layer formation by sputtering and subsequent heat treatment will be described below.

  In the sputtering step, a target composed of a Cu—Ga alloy (Cu50% Ga50at%) was sputtered in the chamber while continuing to supply Ar gas into the chamber, and then a target composed of In metal was sputtered. By this sputtering step, a precursor layer in which a Cu—Ga alloy layer and an In layer were sequentially laminated was obtained. Note that in the sputtering step, the thickness of the Cu—Ga layer was 670 nm, and the thickness of the In layer was 330 nm. Further, in the sputtering process, the substrate temperature was set to 200 ° C., and the flow rate of Ar gas was set so that the atmospheric pressure in the chamber was 1 Pa.

In the heat treatment process after the sputtering process, the precursor layer is selenized by heating the precursor layer for 1 hour in an H ₂ Se atmosphere at 550 ° C., and the first p-type semiconductor layer having a thickness of 2 μm. Formed.

  The second light absorption layer was not provided after the foreign phase removal treatment.

  A solar cell of Comparative Example 12 was produced in the same manner as in Example 26 except for the above items.

  Compound used for p-type light absorption layer, Ib group / IIIb group composition ratio of p-type light absorption layer immediately after film formation, Ib group / IIIb group composition ratio after heterophasic removal treatment, photoluminescence spectrum of p-type light absorption layer Table 15 shows the half-width value of the light emission with the narrowest half-value width in the cathodoluminescence spectrum, the value of k in the measurement of the dependence of the photoluminescence intensity on the excitation light intensity, and the method for removing the different phases.

(Example 44)
The first p-type light absorption layer was formed by the sputtering method and the subsequent heat treatment as in Comparative Example 12.

  A second light absorption layer was formed by the sputtering method in the same manner as in Example 43.

  A solar cell of Example 44 was made in the same manner as in Example 26 except for the above items.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group / IIIb group composition ratio after the heterophase removal treatment, Table 15 shows the half-value width of the light emission with the narrowest half-value width in the photoluminescence spectrum and the cathodoluminescence spectrum of the p-type light absorption layer, and the value of k in the measurement of the excitation light intensity dependence of the photoluminescence intensity, and the method for removing the different phases. Show.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 16 shows the manufacturing method and the film formation temperature.

(Examples 45-49)
The material shown in Table 17 was used for the first p-type absorber layer. In the p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio immediately after the film formation was a value shown in Table 17.

  After the formation of the first p-type light absorption layer, the substrate is immersed in an aqueous potassium cyanide solution (10 wt%) for 5 minutes to remove the Ib group-VIb group compound which is a different phase contained in the first p-type light absorption layer. It was.

  After the heterogeneous phase removal treatment of the first p-type light absorption layer, a second light absorption layer was formed on the first p-type light absorption layer by vacuum deposition.

The substrate was placed in the chamber of the PVD apparatus, and the inside of the chamber was evacuated. The ultimate pressure in the vacuum apparatus was 1.0 × 10 ⁻⁸ torr.

  Then, after the substrate was heated to 200 ° C. and the temperature was stabilized, the shutter of each K cell of In, Ga, and Se was opened to deposit In, Ga, and Se on the substrate. When a layer having a thickness of about 20 nm was formed on the substrate by this deposition, the shutters of the In and Ga K cells were closed. Se continued to supply.

  Thereafter, the substrate was heated to a heat treatment temperature shown in Table 18 in the chamber to perform heat treatment. The heat treatment time was 2 min. Thereafter, the substrate was cooled to 200 ° C., the shutter of the Se K cell was closed, and the formation of the second layer was completed.

  Except for the above items, solar cells of Examples 45 to 49 were produced in the same manner as in Example 26.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group / IIIb group composition ratio after the heterophase removal treatment, Table 17 shows the half-width value of the light emission with the narrowest half-value width in the photoluminescence spectrum and the cathodoluminescence spectrum of the p-type light absorption layer, and the value of k in the measurement of the excitation light intensity dependence of the photoluminescence intensity, and the method for removing the different phases. Show.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 18 shows the manufacturing method and the film formation temperature.

(Examples 50 to 54)
The material shown in Table 17 was used for the first p-type absorber layer. In the first p-type absorber layer film forming step, the flux was set so that the Ib group / IIIb group composition ratio immediately after the film formation was a value shown in Table 17.

  After the formation of the first p-type light absorption layer, the substrate is immersed in an aqueous potassium cyanide solution (10 wt%) for 5 minutes to remove the Ib group-VIb group compound which is a different phase contained in the first p-type light absorption layer. It was.

  Thereafter, the substrate on which the first p-type light absorption layer was formed was placed in a sputtering apparatus, and the second light absorption layer was formed by a sputtering method.

  Details of the formation of the second light absorption layer by sputtering will be described below.

A substrate was placed in the sputtering apparatus, and the inside of the apparatus was evacuated. The ultimate pressure was 1.0 × 10 ⁻⁶ torr. After deaeration, the substrate temperature was kept at room temperature (30 ° C.). After that, while continuing to supply Ar gas into the chamber, a target composed of (In _0.5 Ga _0.5 ) ₂ Se ₃ was sputtered in the chamber to form a film on a substrate placed oppositely.

After film formation, the substrate was transferred to a heat treatment furnace and heat treatment was performed. In the heat treatment step, the substrate was heated at a temperature shown in Table 18 for ₂ minutes in an H ₂ Se atmosphere, thereby forming a second light absorption layer having a thickness of 20 nm. After the heat treatment, the substrate was cooled to 50 ° C. and taken out to finish the second light absorption layer forming step.

  Except for the above matters, solar cells of Examples 50 to 54 were produced in the same manner as in Example 26.

  The compound used for the first p-type light absorption layer, the Ib group / IIIb group composition ratio of the first p-type light absorption layer immediately after film formation, the Ib group / IIIb group composition ratio after the heterophase removal treatment, Table 17 shows the half-width value of the light emission with the narrowest half-value width in the photoluminescence spectrum and the cathodoluminescence spectrum of the p-type light absorption layer, and the value of k in the measurement of the excitation light intensity dependence of the photoluminescence intensity, and the method for removing the different phases. Show.

  Compound used for second light absorption layer, Ib group / IIIb group composition ratio contained in second light absorption layer obtained by AES measurement, film thickness of second light absorption layer, second light absorption layer Table 18 shows the manufacturing method and the film formation temperature.

(Evaluation of thin-film solar cells)
Tables 19 and 20 show the characteristics of the solar cells of Examples 1 to 54 and Comparative Examples 1 to 12.

  A first light absorption layer and a second light absorption layer, wherein the first light absorption layer includes a group Ib element, a group IIIb element, and a group VIb element, and a photoluminescence spectrum or cathodoluminescence. A p-type semiconductor layer having a light emission peak having a half-value width of 1 meV or more and 15 meV or less in the sense spectrum, wherein the second light absorption layer contains a group Ib element, a group IIIb element, and a group VIb element; The conversion ratio of the solar cells of Examples 1 to 54 in which the composition ratio of the element and the group IIIb element is 0.1 or more and less than 1.0 and provided on the light incident surface side of the first light absorption layer is It was confirmed that it was larger than Comparative Examples 1 to 12 that did not include the first p-type light absorption layer or the second light absorption layer.

  A first light absorption layer and a second light absorption layer, wherein the first light absorption layer includes a group Ib element, a group IIIb element, and a group VIb element, and a photoluminescence spectrum or cathodoluminescence. A p-type semiconductor layer having a light emission peak having a half-value width of 1 meV or more and 15 meV or less in the sense spectrum, wherein the second light absorption layer contains a group Ib element, a group IIIb element, and a group VIb element; The open-circuit voltage of the solar cells of Examples 1 to 6 in which the composition ratio of the element and the group IIIb element is 0.1 or more and less than 1.0, and provided on the light incident surface side of the first light absorption layer; The conversion efficiency includes a group Ib element, a group IIIb element, and a group VIb element, and the half width in the photoluminescence spectrum or cathodoluminescence spectrum is 1 meV or more and 15 m. A solar cell of Comparative Example 1 that includes a first p-type semiconductor layer including an emission peak of V or less but does not include a second light absorption layer, and includes a group Ib element, a group IIIb element, and a group VIb element The first p-type light-absorbing layer has a second light-absorbing layer on the first p-type light-absorbing layer, the composition ratio of the group Ib element and the group IIIb element being 0.1 or more and less than 1.0. It was confirmed that the half width in the photoluminescence spectrum or cathodoluminescence spectrum of the light absorption layer was larger than that of the solar cell of Comparative Example 2 having 40 meV outside the range of 1 meV to 15 meV.

  A first light absorption layer and a second light absorption layer, wherein the first light absorption layer includes a group Ib element, a group IIIb element, and a group VIb element, and includes a group Ib element / group IIIb Examples 2 to 5 and Examples 7 to 54, which are p-type semiconductor layers having an element ratio of 1.00 and including a light emission peak having a half width of 1 meV or more and 15 meV or less in the photoluminescence spectrum or cathodoluminescence spectrum The open-circuit voltage and conversion efficiency of a solar cell include a group Ib element, a group IIIb element, and a group VIb element, and a p-type semiconductor including a light emission peak having a half width of 1 meV or more and 15 meV or less in a photoluminescence spectrum or cathodoluminescence spectrum Although it is a layer, the ratio of the group Ib element / group IIIb element is not 1.00, which is larger than those of Example 1 and Example 6. It has been confirmed.

  A first light absorption layer and a second light absorption layer, wherein the first light absorption layer includes a group Ib element, a group IIIb element, and a group VIb element, and includes a group Ib element / group IIIb A first p-type light absorption layer which is a p-type semiconductor layer having an element ratio of 1.00 and having a light emission peak having a half-value width of 1 meV or more and 15 meV or less in a photoluminescence spectrum or a cathodoluminescence spectrum; , A group IIIb element, and a group VIb element, and a composition ratio of the group Ib element to the group IIIb element is 0.1 or more and less than 1.0 on the first p-type light absorption layer The open-circuit voltage and conversion efficiency of the solar cells of Examples 7 to 14 included in the solar cell of Comparative Examples 3 to 4 in which the composition ratio of the Ib group element and the IIIb group element included in the second layer is outside the above range. It is confirmed that it is bigger than It was.

  Light emission including various group Ib elements, group IIIb elements, and group VIb elements, the ratio of group Ib elements / group IIIb elements is 1.00, and the half-value width is 1 meV or more and 15 meV or less in the photoluminescence spectrum or cathodoluminescence spectrum A first p-type absorber layer that is a p-type semiconductor layer including a peak, a group Ib element, a group IIIb element, and a group VIb element, and a composition ratio of the group Ib element to the group IIIb element is 0.1 or more and 1 The open-circuit voltage and conversion efficiency of the solar cells of Examples 15 to 21 provided with the second light-absorbing layer that is less than 0.0 on the first p-type light-absorbing layer have the same composition, the same photoluminescence, or Although the first p-type light absorption layer having the emission half-value width of the cathodoluminescence spectrum is provided, the thicknesses of Comparative Examples 5 to 11 having no second light absorption layer It was confirmed to be larger than the positive battery.

  Light emission including various group Ib elements, group IIIb elements, and group VIb elements, the ratio of group Ib elements / group IIIb elements is 1.00, and the half-value width is 1 meV or more and 15 meV or less in the photoluminescence spectrum or cathodoluminescence spectrum Example in which first p-type light absorption layer, which is a p-type semiconductor layer including a peak, and the same Ib group element and IIIb group element as the first p-type light absorption layer are used for the second light absorption layer The open circuit voltage and the conversion efficiency of the solar cells 22 and 25 are the first p-type light-absorbing layers having the same composition, the same photoluminescence or cathodoluminescence spectrum emission half width, respectively. Compared with the solar cells of Examples 23 and 24, in which a Group Ib element or Group IIIb element different from the light absorption layer was used for the second light absorption layer, It was confirmed.

  First p-type light absorption, which is a p-type semiconductor layer having an lb group element / IIIb group element ratio of 1.00 and a light emission peak having a half-value width of 1 meV to 15 meV in the photoluminescence spectrum or cathodoluminescence spectrum And the same Ib group element and IIIb group element as the first p-type light absorption layer in the second light absorption layer, and the composition ratio of the plurality of group IIIb elements is the first p-type light absorption layer The open-circuit voltage and conversion efficiency of the solar cell of Example 26 having the same second light absorption layer as that of the first p-type light absorption is the composition ratio of the plurality of group IIIb elements contained in the second layer. Compared with Example 27 different from the layer, it was confirmed to be large.

  Cu, a group IIIb element, and a group VIb element, a composition ratio of Cu and a group IIIb element is 1.00, and includes a light emission peak having a half-value width of 1 meV or more and 15 meV or less in a photoluminescence spectrum or a cathodoluminescence spectrum. a first p-type light-absorbing layer that is a p-type semiconductor layer, Cu, a group IIIb element, and a group VIb element, and a composition ratio of Cu and the group IIIb element is 0.1 or more and less than 1.0 The conversion efficiency of the solar cell of Example 28 provided with two light absorption layers on the first p-type light absorption layer is that of the solar cell of Example 29 in which the Ib element contained in the light absorption layer and the second layer is not Cu. It was confirmed that it was larger than the battery.

  It contains an Ib group element, an IIIb group element, and a VIb group element, the composition ratio of the Ib group element and the IIIb group element is 1.00, and the half width in the photoluminescence spectrum or cathodoluminescence spectrum is 1 meV or more and 15 meV or less A first p-type absorber layer that is a p-type semiconductor layer including an emission peak, a group Ib element, a group IIIb element, and a group VIb element, and a composition ratio of the group Ib element and the group IIIb element is 0.1 or more The sun of Examples 31-35, in which a second light absorption layer that is less than 1.0 is provided on the first p-type light absorption layer, and the film thickness of the second light absorption layer is 1 nm or more and 100 nm or less. It was confirmed that the open circuit voltage and the conversion efficiency of the battery were larger than those of the solar cells of Examples 30 and 36 whose film thickness was outside the above range.

で表したとき ｋの値が１＜ｋ＜２の範囲内である実施例１〜６の太陽電池の開放電圧および変換効率は、前記範囲外である比較例２の太陽電池にくらべ、大きいことが確認された。 When the excitation light dependency or excitation electron beam intensity dependency is measured in the photoluminescence measurement, the relationship between the excitation light intensity or excitation electron beam intensity I _ex ^k and the photoluminescence intensity I _PL is expressed by the following equation (2):

The open-circuit voltage and conversion efficiency of the solar cells of Examples 1 to 6 in which the value of k is in the range of 1 <k <2 are larger than the solar cell of Comparative Example 2 that is outside the above range. Was confirmed.

  In the step of forming the first p-type absorber layer, after forming a film so that the ratio of the group Ib element to the group IIIb element is larger than 1.0, the heterogeneous group Ib-VIb group compound is removed. It was confirmed that the open-circuit voltage and conversion efficiency of the solar cells of Examples 38 to 41 including the steps were larger than those of the solar cell of Example 37 not including the heterogeneous phase removal step.

  DESCRIPTION OF SYMBOLS 2 ... Conventional solar cell, 4 ... Solar cell which concerns on one Embodiment of this invention, 6 ... Soda lime glass, 8 ... Back electrode layer, 10 ... p-type light absorption layer, 12 ... second layer, 14 ... n-type semiconductor layer, 16 ... semi-insulating layer, 18 ... window layer (transparent conductive layer), 20 ... upper electrode (extraction electrode).

Claims (8)

Having a first light absorbing layer and a second light absorbing layer,
The first light absorption layer is a p-type semiconductor layer that includes a group Ib element, a group IIIb element, and a group VIb element, and includes a light emission peak having a half-value width of 1 meV to 15 meV in a photoluminescence spectrum or a cathodoluminescence spectrum. Yes,
The second light absorption layer includes a group Ib element, a group IIIb element, and a group VIb element, and a composition ratio of the group Ib element to the group IIIb element is 0.1 or more and less than 1.0, Provided on the light incident surface side of one light absorption layer,
A solar cell characterized by that.   2. The solar cell according to claim 1, wherein the composition ratio of the Ib group element and the IIIb group element contained in the first light absorption layer is 1.0.   The Group Ib element and Group IIIb element contained in the second layer formed on the first light absorption layer are the same as the Group Ib element and Group IIIb element contained in the first light absorption layer The solar cell according to any one of claims 1 and 2.   The solar cell according to claim 1, wherein the group Ib element contained in the first light absorption layer and the second light absorption layer is Cu.   The thickness of the 2nd light absorption layer formed on said 1st light absorption layer is the range of 1 nm or more and 100 nm or less, The solar cell as described in any one of Claims 1-4 characterized by the above-mentioned.   A layer formed by removing the Ib group-VIb group compound which is a different phase after forming so that the ratio of the Ib group element to the IIIb group element is larger than 1.0 is used as the first light absorption layer. The solar cell as described in any one of Claims 1-5.   The method for producing a solar cell according to any one of claims 1 to 6, wherein the second light absorption layer is formed by a kind of method selected from a vacuum deposition method and a sputtering method.   The second layer is formed by performing a heat treatment in a subsequent process in addition to a kind of method selected from a vacuum deposition method and a sputtering method. A method for manufacturing a solar cell.

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